I do partial water changes once a week. I feed him a pinch of Betta pellets twice a day and sometimes add a few flakes, but he doesn't seem to like the flakes at all.

I do plan to upgrade to live plants sometime soon, but wondered if there was anything else I should change?

Also, I know there's a separate forum for this so I don't need specific recommendations, but do you think it would be better to add a tankmate of some sort? (be it fish, snail, etc.) or just let Brucie have the tank to himself?

I think that you have done great so far! A 10 gallon tank is very spacious for one betta and that is a good thing. You don't really have to add anything unless you want to. Brucie would probably love to have the tank to himself but if you wanted a snail he would not mind or attack it. Make sure you are not overfeeding. If your betta pellet instructions say to feed as much as your fish will eat in 1-2 minutes or somehitng like that don't believe it. Bettas would keep eating. I feed 3-4 pellets twice daily but it depends on your pellet size. If your bettas tummy looks a little fat you could give one less pellet or you can pick one day of the week where you don't feed him at all. Like I said, you are doing great and your betta must be very happy :) If you do get live plants make sure you quarantime them in tap water first so the chlorine from your tap will kill all the snails. Trust me you don't want snails lol.